A former aide to Richmond Mayor Gayle McLaughlin is under investigation for allegedly misusing a pair of city credit cards to drain about $50,000 from an office fund, officials said Friday.

Parin Shah, who worked for more than a year as a top policy aide to McLaughlin, was let go by the city in February after an internal city audit revealed the discrepancy in the mayor's special fund-raising account. The fund is used for programs designated by the mayor, McLaughlin said.

This week, Contra Costa County District Attorney Robert Kochly lifted a confidentiality request and allowed the mayor to talk about the incident, McLaughlin said.

No charges have been filed against Shah, said Deputy District Attorney Steve Bolen, who said the investigation is continuing and declined to discuss details.

Shah "managed the expenses for the office," said the mayor, who had hired him. "To learn something like this about a trusted aide is very distressing."

Shah had turned in his resignation for unrelated reasons when McLaughlin heard from the auditors. She said she called Shah into her office and told him that his resignation was accepted, effective immediately.

"I confronted him with the audit reports and he had no good explanation," McLaughlin said. The matter was quickly referred to the district attorney's office.

Shah now works as local policy director of Green For All, an Oakland group working to improve low-income communities by moving the nation toward green energy and environmentally friendly jobs. He did not respond to a message left on his office voice mail.